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United States Patent |
5,127,499
|
Beccaris
,   et al.
|
July 7, 1992
|
Clutch having a pressure plate associated with an intermediate disc
Abstract
A clutch includes a reaction plate, a cover plate, a pressure plate and,
arranged between the pressure and reaction plates, at least one friction
disc. At least one intermediate disc is also provided, being arranged to
come into contact with the pressure plate. The pressure plate and the
adjacent intermediate disc associated with the pressure plate are secured
together by a resilient gripping action, which is exerted by axial
gripping members arranged between the pressure plate and the intermediate
plate.
Inventors:
|
Beccaris; Carlo (Santena, IT);
de Briel; Jacques T. (Levallois Perret, FR)
|
Assignee:
|
Valeo (Paris, FR)
|
Appl. No.:
|
709027 |
Filed:
|
May 31, 1991 |
Foreign Application Priority Data
| May 31, 1990[FR] | 90 06764 |
| Nov 28, 1990[FR] | 90 14870 |
Current U.S. Class: |
192/70.27; 192/70.19; 192/89.1 |
Intern'l Class: |
F16D 013/50 |
Field of Search: |
192/70.27,70.11,89 B,70.19
|
References Cited
U.S. Patent Documents
1016427 | Feb., 1912 | Morse | 192/70.
|
1665999 | Apr., 1928 | Byerlein | 192/70.
|
2190874 | Feb., 1940 | Jarrett | 192/113.
|
3236347 | Feb., 1966 | Puls et al. | 192/70.
|
4236620 | Dec., 1980 | Beccaris | 192/70.
|
4368810 | Jan., 1983 | Maucher et al. | 192/70.
|
Foreign Patent Documents |
2155123 | May., 1972 | DE.
| |
2623862 | Jun., 1989 | FR.
| |
60-188628 | Sep., 1985 | JP | 192/70.
|
752516 | Jul., 1956 | GB.
| |
Primary Examiner: Braun; Leslie A.
Assistant Examiner: Pitts; Andrea
Attorney, Agent or Firm: Longacre & White
Claims
What is claimed is:
1. A clutch comprising: a reaction plate; a cover plate secured to said
reaction plate; a pressure plate; means mounting the pressure plate to the
cover plate for rotation with the latter but for axial movement with
respect to the cover plate; a hub mounted coaxially with said reaction and
pressure plates; at least one friction disc secured to the hub for
rotation therewith; at least one intermediate disc; and means mounting the
at least one intermediate disc for axial movement with respect to the
cover plate and for rotational movement with the reaction plate and cover
plate, the at least one friction disc and the at least one intermediate
disc being disposed between the pressure plate and the reaction plate with
an associated intermediate disc, in contact with the pressure plate,
wherein the clutch further comprises axial fastening means arranged
between the pressure plate and its associated intermediate disc to exert a
resilient gripping action thereon.
2. A clutch according to claim 1, wherein the axial fastening means are
formed as a centering means.
3. A clutch according to claim 2, wherein the axial fastening means include
at least a fastening device having a centering member carried by the
intermediate disc associated with the pressure plate, the latter having an
oblong hole formed therein and the centering member passing through the
oblong hole.
4. A clutch according to claim 3, wherein the oblong hole defines an axis
of symmetry extending through the center of rotation of the pressure
plate.
5. A clutch according to claim 4, wherein the centering member is adapted
to cooperate with lateral flanks of the oblong hole.
6. A clutch according to claim 3, wherein the centering member constitutes
a spacing means and has a shoulder, the clutch further comprising axially
acting resilient means interposed axially between said shoulder and the
pressure plate, for engagement with said shoulder whereby to grip the
pressure plate and its associated intermediate disc resiliently together.
7. A clutch according to claim 6, further comprising a tenon carried by
said intermediate disc associated with the pressure plate, said centering
member being carried by said tenon, the pressure plate having a radial ear
and said oblong hole being formed in said ear.
8. A clutch according to claim 7, further comprising an intermediate
driving crown member secured with respect to the reaction plate and a
plurality of axial lugs carried by the intermediate driving crown member,
with each said axial lug defining a mortice, said tenon of the
intermediate disc associated with the pressure plate cooperating with one
of said mortice.
9. A clutch according to claim 3, wherein said centering means comprise a
centring tube, a tubular rivet having a head and extending through the
centering tube, and a ring held by the head of the tubular rivet in
contact with said intermediate disc associated therewith.
10. A clutch according to claim 1, wherein the cover plate is formed with a
skirt portion having holes formed therein, the pressure plate having
channels formed on its face adjacent to the intermediate disc associated
with the pressure plate and being open in line with said holes in the
skirt portion of the cover plate.
11. A clutch according to claim 3, further including axially and
progressively acting resilient means interposed axially between the
pressure plate and said intermediate disc associated with the pressure
plate, said axially and progressively acting resilient means being mounted
by said centering means whereby to obtain progressive engagement of the
clutch.
12. A clutch according to claim 11, wherein said axially and progressively
acting resilient means comprise a resilient, corrugated ring having radial
lugs projecting from its outer periphery, for mating cooperation with said
centering members, each said lug having a hole formed therethrough and
each said centering member extending through a corresponding one of said
holes in the lugs of the corrugated ring.
13. A clutch according to claim 12, wherein the corrugated ring comprises
first radial portions and second radial portions alternating with the
first radial portions, for contact with the pressure plate and the
intermediate disc adjacent to the pressure plate, the corrugated ring
further having oblique folds through which its said lugs are joined
Description
FIELD OF THE INVENTION
This invention relates to clutches of the kind having a plurality of
friction discs, especially for motor vehicles. More particularly, the
field of the invention is that of clutches of the above kind comprising: a
reaction plate; a cover plate which is secured to the reaction plate; a
pressure plate which is fixed with respect to the cover plate to the
extent that it rotates with the latter, but which is mounted for axial
movement with respect to the cover plate; and, arranged between the
pressure plate and the reaction plate, firstly at least one friction disc
mounted for rotation with a hub, and secondly at least one intermediate
disc which is mounted for rotation with the reaction plate and the cover
plate, with the intermediate disc, or one of the intermediate discs if
there is more than one, being adjacent to the pressure plate.
BACKGROUND OF THE INVENTION
A clutch of the above kind is described in the specification of French
published patent application FR No. 2 623 862A. In that specification, the
intermediate discs are coupled with the reaction plate for rotation with
the latter, the intermediate discs being movable axially by virtue of a
plurality of intermediate driving members in the form of spacing blocks.
Such an arrangement enables a cover plate of a standard type to be used.
However, the intermediate disc which lies adjacent to the pressure plate
is not located against axial movement with respect to the pressure plate.
At the instant when the clutch is disengaged during a declutching
operation, and during the withdrawal or retraction of the pressure plate,
this results in a loss of travel for the friction disc or discs, with the
latter not becoming spaced apart by a sufficiently large distance from the
intermediate discs.
DISCUSSION OF THE INVENTION
An object of the present invention is to overcome the above drawbacks, and
to provide a clutch arrangement in which the intermediate disc adjacent to
the pressure plate has a sufficiently large degree of displacement, while
also giving other advantages.
In accordance with the invention, a clutch of the kind having a plurality
of friction discs, comprising: a reaction plate; a cover plate secured to
the reaction plate; a pressure plate which is mounted for rotation with
the cover plate and for axial movement with respect to the latter; at
least one friction disc which is mounted between the pressure plate and
the reaction plate and which is also mounted on a hub for rotation with
the latter; at least one intermediate disc, disposed between the pressure
plate and the reaction plate and mounted for rotation with the reaction
plate and the cover plate while being movable axially with respect to the
pressure plate and reaction plate, the said intermediate disc (or one of
them if more than one is provided) being in contact with the pressure
plate, is characterised in that axial securing means are arranged between
the pressure plate and its associated intermediate plate, so as to grip
the said pressure plate and intermediate plate resiliently.
In a clutch according to the invention, during the declutching operation
the intermediate disc adjacent to the pressure plate follows the movement
of the latter in such a way that the friction disc or discs are able to be
displaced by a satisfactory amount. In addition, the number of components
to be assembled together is reduced, with the pressure plate constituting,
with its associated intermediate disc, a sub-assembly which is readily
able to be handled and transported.
In addition, the resilient gripping action mentioned above enables the
clutch to reach high temperatures without this giving rise to any problem.
It also enables the pressure plate and its associated intermediate disc to
be made in different materials. For example, the pressure plate may be of
aluminum, while the intermediate disc is of a carbon based material.
In practice, it therefore becomes possible to accommodate thermal expansion
and contraction which arises due to the difference in temperature between
the intermediate disc and the pressure plate, while also providing a
clutch the components of which have low inertia.
In accordance with a feature of the invention, the said axial securing
means are arranged for centering the pressure plate in such a way that the
latter is able to be movable axially while being coupled in rotation to
the cover plate and to the reaction plate and also being centered. The
pressure plate is thus coaxially suspended on its intermediate disc.
All of the above configurations are of advantage when the intermediate disc
is driven by an intermediate driving member which couples it in rotation
with axial mobility, to the cover plate and to the reaction plate. In that
case, the intermediate member need not be elongated, since it drives the
pressure plate in rotation through its intermediate disc.
In accordance with a feature of the invention which is especially
preferred, the said securing means include at least one securing device
having at least one axially acting resilient means and passing through the
pressure plate via an oblong hole formed in the latter, the said hole
being radially oriented. This arrangement minimizes any danger of
deterioration of the intermediate disc, since the latter can easily expand
or contract radially and axially with respect to its pressure plate.
The intermediate driving member is preferably so designed as to have axial
retaining means for an intermediate disc adjacent to the reaction plate.
This produces a satisfactory degree of displacement for the friction
discs.
All of the above arrangements enable resilient means, of the kind that
exert a progressive axial force, to be mounted between the pressure plate
and its associated intermediate disc, and also between the reaction plate
and its associated intermediate disc. This progressive axial force results
in improved comfort to the occupants of the vehicle.
The description which follows illustrates the invention in detail, by way
of example only and with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view in elevation of the clutch in accordance with the
invention.
FIG. 2 is a view in cross section taken on the line 2--2 in FIG. 1.
FIG. 3 is a view as seen in the direction of the arrow 3 in FIG. 1.
FIG. 4 is a view in cross section, showing part of the clutch, the cross
section being taken on the line 4--4 in FIG. 2.
FIG. 5 is a detail view showing the form of the notch formed in the
intermediate crown on the clutch.
FIG. 6 is a simplified perspective view showing the intermediate discs, the
friction discs, the intermediate crown and the reaction plate of the
clutch in accordance with the invention.
FIG. 7 is a view in cross section showing the securing means whereby the
pressure plate is attached to its associated intermediate disc.
FIG. 8 is a partial view, seen in cross section on the line 8--8 in FIG. 7,
with the intermediate crown included.
FIG. 9 is a partial view similar to FIG. 2, but showing a modification
having resilient rings for exerting a progressive axial thrust.
FIGS. 10 to 12 are views similar to FIGS. 5 to 8 respectively, but showing
the modified embodiment seen in FIG. 9.
FIG. 13 is a perspective view of the progressive thrust ring itself.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The clutch which will be described below is a clutch of the kind having two
friction discs, particularly suitable for fast motor vehicles such as
sports or racing cars. It comprises a plurality of annular members, all
coaxial with each other, namely a reaction plate 1, a cover plate 2, an
intermediate crown 3, a diaphragm 4, intermediate discs 6, 7 and 8,
friction discs 9 and 10, and a hub 11. The reaction plate 1 is also the
engine flywheel, and is fastened to the crankshaft (not shown) of the
engine of the vehicle, in this particular example by means of bolts or
studs 12 which are shown diagrammatically.
The cover plate 2 is generally in the form of a hollow dish, and has an
outwardly projecting radial fastening flange 21 which is joined to an
annular skirt portion 22 oriented axially. The skirt portion 22 is joined
to a base portion 23 which extends generally radially and towards the axis
of the assembly. The base portion 23 has a projecting bead 24, and is also
provided with assembly tabs 25. It has a central opening. The bead 24 acts
as a primary stop element for the diaphragm 4. More precisely, the
diaphragm 4 has a peripheral portion 41 defining a Belleville ring, and a
central portion which is divided into radial fingers 42 separated by gaps
(see FIG. 1), together with apertures 43 adjacent to the roots of the
fingers 42, with the gaps between the fingers opening into the apertures
43.
The Belleville ring 41 bears internally on the annular bead 24, while
externally the ring 41 bears on an annular lip 51 of the pressure plate 5.
In this example, the annular lip 51 is divided into separate sections. The
assembly tabs 25 extend through the apertures 43 of the diaphragm, being
then bent radially outwards in the direction away from the axis of the
assembly, so that they are hook-shaped. The purpose of the tabs 25 is to
locate in position a sealing ring 14. This ring 14 constitutes a secondary
engagement element for the Belleville ring 41, facing the bead 24.
In this way, the diaphragm 4 is mounted for tilting movement on the cover
plate 2, and bears on the latter so as to urge the pressure plate 5
towards the reaction plate 1, thereby enabling the discs 6 to 10 to be
gripped. More precisely, the intermediate disc 6, the friction disc 10,
the intermediate disc 7, the friction disc 9, and the intermediate disc 8
are interposed in axial succession, in the order mentioned, between the
reaction plate 1 and the pressure plate 5.
The discs 6, 7 and 8, which in this example are driving discs, are secured
to the reaction plate 1 and the cover plate 2, for rotation with them,
through the crown 3 which thus acts as an intermediate drive member. The
discs 9 and 10, which in this example are driven discs, being arranged
alternately with the intermediate discs 6, 7 and 8, are mounted so as to
be rotatable with the hub 11 while being movable axially. They are
surrounded by the skirt portion 22 of the cover plate 2, by the discs 7
and 8, and by the pressure plate 5.
The crown 3 has means for coupling it in rotation, so as to drive the
intermediate discs 7 and 8 while preserving their ability to move in the
axial direction. In this example, this rotary coupling means consists of a
plurality of axial lugs 32, fixed to the crown 3 (see FIGS. 3 and 6). Each
lug 32 defines a mortice 36. The lugs 32 extend axially towards the base
portion 23 of the cover plate, the mortices 36 being open towards the base
portion and closed by a ring 31 of the crown 3. A plurality of tenons 71,
81 are arranged to cooperate with the mortices 36. These tenons 71 and 81
are carried by, and project radially from, the respective intermediate
discs 7 and 8, see FIG. 6.
The lugs 32 are fixed to the closure ring 31 (and in this example they are
integral with it). The ring 31 is inserted axially between the reaction
plate 1 and the fastening flange 21 of the cover plate 2. The outer
diameter of the closure ring 31 is, in this example, equal to the outer
diameter of the fastening flange 21 of the cover plate 2. In this example,
the lugs 32 are made integral with the closure ring 31, being formed
simultaneously with it by moulding or casting.
In a modification, the lugs 32 may be separate elements mounted on the
closure ring 31, for example by welding, or by the use of screws or any
other suitable type of fastener.
Referring to FIG. 3, the cover plate 2 is of a standard type, with its
skirt portion 22 being provided with openings 27, each of which is
delimited by a radial hood portion 28. The hood portion 28 is joined to
the fastening flange 21, and would normally serve for securing tangential
tongues which couple the pressure plate to the cover plate for rotation
with it. In the present case, however, use is made of the opening 27 for
insertion of the axial lugs 32, these lugs being designed and dimensioned
accordingly.
The intermediate driving member or crown 3 has at least one thrust surface
35 (see FIGS. 5 and 6) which faces towards the reaction plate 1, while the
intermediate disc 6 adjacent to the reaction plate 1 has a cooperating
reaction surface 61, which engages the thrust surface 35 so as to locate
the intermediate disc 6 axially with respect to the reaction plate 1. In
this example, the intermediate disc 6 has at least one reaction surface 61
which cooperates with a notch 33 formed in the closure ring 31, on the
side of the latter which faces axially towards the reaction plate 1. The
thrust surface 35 is formed in the notch 33 itself, while the reaction
surface 61 is formed on a projecting tenon of the intermediate disc 6.
It will be noted that in this example, each intermediate disc has three
tenons which are spaced apart circumferentially at 120.degree. with
respect to each other. It will also be noted that the cover plate 2 has
three hood portions 28 and three openings 27. The crown 3 has three axial
lugs 32, three mortices 36, and three notches 33.
The outer diameter of the discs 6 to 10 determines the internal diameter of
the closure ring 31 and of the lugs 32, according to requirements, but in
such a way that, in particular, the discs 7 to 10 are able to penetrate
within the circular envelope defined by the lugs 32, while the
intermediate disc 6 can penetrate into the interior of the closure ring
31.
In this example the closure ring 31 is of metal. The notches 33 may be
formed by a milling operation, and may extend through the whole radial
height of the closure ring 31. The shape of the notches 33 depends on that
of the tenons of the intermediate disc 6.
The number of tenons 81, mortices 36, notches 33 and hood portions 28
depends on the requirements of the application to which the clutch is to
be put, and on the size of the cover plate 2. The same is true of securing
means indicated at 15 in FIGS. 3 and 4. There may however be more than
three of each of these elements. It is even possible to differentiate
between the intermediate disc 6 on the one hand and the other discs 7 and
8 on the other hand, by providing a number of notches 33 that is different
from the number of mortices 36. The tenons of the discs 6, 7 and 8 overlap
the notches 33 and mortices 36 radially in this example. The notches 33
are here arranged at the level of (i.e. in circumferential alignment with)
the lugs 32, which have two lateral shouldered portions 34 to support the
heads of screws 16 securing the crown 3 to the reaction plate 1. The
mechanical strength of the crown 3 is thus able to be made satisfactory
despite the presence of the notches 33. In addition, because of the screws
16 and notches 33, it is possible to build a sub-assembly consisting of
the crown 3, the intermediate disc 6 and the reaction plate 1, thus
enabling the intermediate disc 6 to be inspected.
The cover plate 2 is also secured to the reaction plate 1 by means of
screws (not shown), which extend through holes 29 in the fastening flange
21 of the cover plate, and through corresponding hole formed in the
closure ring 31 (see FIG. 3).
The notch 33 has a base portion which is joined through rounded portions 35
to two axially disposed side flanks of the notch, and is generally
U-shaped. The projecting tenon 61 has a circumferential width, subject to
fitting clearances, equal to the distance separating the side flanks of
the notch 33. Its thickness is less than the depth of the notch 33, so
that a clearance J (FIG. 5) exists between the base of the notch 33 and
the tenon 61 with its inclined flanks. The edges of the tenon 61
constitute stop or reaction surfaces and are inclined at sharp angles.
They are designed so as to cooperate with the rounded portions
constituting the actual working part of the latter.
The face of the intermediate disc 6 and the face of the intermediate crown
3 that face towards the reaction plate 1 lie in the same plane. Thus,
during assembly by tightening the screws 16 into the reaction plate 1, the
crown 3 is offered up to the reaction plate 1 so that the tenon 61 comes
to bear on the rounded stop surfaces 35. In this way, the intermediate
disc 6 is located axially without any play, but with coupling in rotation.
Since the clutch is intended for use in a fast motor vehicle such as a
racing or sports car, the intermediate discs 6, 7 and 8 in this example
contain carbon as do the friction discs 9 and 10. The latter are coupled
to the hub 11 through teeth 91 and 101 (see FIGS. 6 and 4), which engage
in complementary axial grooves 117 formed in the hub 11.
The hub 11 has an integral central portion with a splined internal bore,
for mounting it on the input shaft (not shown) of the gearbox of the
vehicle, for rotation with the input shaft. This central portion carries a
radial web 111, which itself carries a fork 112 having two branches spaced
apart from each other and extending radially outwards. The branches of the
fork 112 are separated by a groove or gap 118. The width of each branch of
the fork is greater than the thickness of the thickened inner periphery of
the friction disc 10 or 9 concerned. The branches of the fork 112 are
provided with grooves 117, with which the teeth 91 and 101 of the friction
discs 9 and 10 respectively are arranged to cooperate. In order to
facilitate machining, the grooves 117 are aligned axially from one branch
of the fork to the other. Machining is then carried out by axial traverse
of the fork 112.
It will be noted that in this example, the teeth 91 and 101 are trapezoidal
in shape, and that the grooves 117 are of the same shape. The grooves 117
are bounded by projections 116 (which are here radial), while the teeth 91
and 101 are bounded respectively by recesses 92 and 102.
Each of four of the projections 116 accomodates one of four rivets 114, for
which purpose they have apertures through which the rivets 114 can pass.
The head of each rivet 114 bears on the surface of the branch that faces
towards the other branch of the fork. The rivet head thus lies in the
groove 118. Besides accommodating the rivet heads, the groove 118 also
enables the inertia of the hub 11 to be reduced. The rivets 114 are
hollow, and extend through the corresponding branch of the fork 112. The
other end of each rivet is upset so as to retain a ring 113 in contact
with the corresponding axial end face of the fork 112.
In this instance, each branch of the fork 112 is provided with two of the
rings 113 and two rivets 114. The rings 113 define shoulders which are
adapted to cooperate respectively with the disc 9 and the disc 10. In a
modification, the rings 113 may be carried by bolts extending through the
fork 112.
Due to the above arrangement, the hub 11 is located axially by the friction
discs 9 and 10, so that during the assembly operation, while the input
shaft of the gearbox is being inserted in the hub, there is no dange of
the hub being ejected.
In addition, the rings 113 enable the movement of the friction discs 9 and
10 to be limited during a declutching operation. This enables the discs 9
and 10 to be displaced by a satisfactory amount. Furthermore, it also
enables a sub-assembly, readily able to be handled and transported, to be
built. This sub-assembly comprises the friction disc 9, 10 and the
intermediate disc 7. All of this simplifies the clutch assembly operation.
The securing means 15, mentioned and seen in FIGS 3 and 4, comprise axial
securing means having a resilient gripping action, and are mounted between
the pressure plate 5 and its associated intermediate disc 8. These axial
securing means comprise, in this example, at least one axial fastening
device 15 inserted in a hood portion 28. The intermediate disc 8 adjacent
to the pressure plate 5 is joined to the latter through at least one of
these fastening devices 15. It is the fastening devices 15 themselves that
exert the appropriate resilient gripping force. They are fitted in
respective tenons 81 of the intermediate disc 8. One fastening device 15
is associated with each tenon 81, as can be seen in FIG. 1. The number of
the fastening devices 15 can of course, if desired, be smaller than the
number of tenons 81.
Referring to FIGS. 7 and 8, in this example the pressure plate 5 has three
ears 53, trapezoidal in shape and projecting radially outwardly from the
outer periphery of the pressure plate. These ears 53 lie in line with the
corresponding tenons 81 of the intermediate disc 8, as can be seen best in
FIG. 8. In this example there are three fastening devices 15 (FIG. 1) and
three ears 53. The fastening devices 15 are spaced apart circumferentially
at regular intervalsk, each in association with a respective one of the
hood portions 28.
As in best seen in FIGS. 7 and 8, each of the three fastening devices 15
comprises a ring 152 and a tubular rivet 151, which passes through a
centering and spacing tube 153 having a shoulder 157 at one of its ends.
The tube 153 and the rivet 151 pass through an opening 155 which is formed
in the tenon 81, and a hole 156 which is formed through the ear 53. The
fastening device 15 also includes an axially acting resilient means 154,
which in this example is a Belleville ring. The latter bears, firstly on
the face of the ear 53 which is directed towards the diaphragm 4 (and
therefore towards the base portion 23 of the cover plate 2), and secondly
on the shoulder 157 of the tube 153.
Instead of th Belleville ring 154, this resilient means could instead
consist of a coil spring or a corrugated ring, for example of
figure-of-eight form.
The other end of the tube 153 is in contact with the ring 152, bearing
against the face of the tenon 81 which is directed away from the ear 53,
and therefore facing towards the reaction plate 1.
The ring 152 is held in position by the upset end of the expandable rivet
151. The head of the latter is shouldered and is in contact with the
shouldered end 157 of the tube 153, while the main portion or shank of the
rivet 151 passes through the tube 153.
The hole 156 in the ear 53, which in this example is narrower in the
circumferential direction than the tenon 81, is oblong in shape, with
parallel side edges extending radially and joined to each other through
rounded base portions. The axis of symmetry of the hole 156 passes through
the centre of rotation of the pressure plate 5, and the tube 153 is in
point contact with the side edges of the holes 156. The pressure plate is
thus centred with respect to the axis of the assembly, by virtue of the
tube 153 cooperating with the contour of th hole 156, together with the
tenon 81 which is centred by the axial lugs 32 (FIG. 3). The pressure
plate 5 is butted against the intermediate disc 8, which enables the
length of the lugs 32 to be reduced.
The tenons 81 are themselves in cooperation with the mortices 36 of the
crown 3. Accordingly, the pressure plate 5 is movable axially with respect
to the cover plate 2, while being coupled to the latter, for rotation with
it, by means of the tenons 81 and tubes 153.
The intermediate disc 8 is made of a carbon based material, while the
pressure plate 5 is for example made of aluminium. By virtue of the
shouldered tube 153, the resilient means 154 and the hole 156, it becomes
possible to absorb any differential thermal expansion or contraction that
may arise due to differences in temperature between the intermediate disc
8 and the pressure plate 5.
The dimensions and stiffness of the resilient mean 154 are selected with a
view to retaining the pressure plate against the intermediate disc 8,
without a clearance between them, when the clutch is operating, while
still enabling the Belleville ring or other resilient means 154 to yield
axially in order to accomodate thermal movement of the pressure plate 5.
The length of the shouldered tube 153 is also selected accordingly, in
such a way that in its compressed position, the resilient means 154 will
exert a sufficiently large thrust to hold the pressure plate 5 and the
intermediate disc 8 together without a clearance between them.
This arrangement is of particular advantages in a sports or racing car or
other high speed motor vehicle, because the clutch is able to reach high
temperatures without any risk of undue deterioration of the friction
discs, while at the same time the inertia is low. By virtue of the
arrangement described above, the pressure plate 5 is resiliently butted
against the intermediate disc 8, without any clearance appearing between
them during the retraction of the intermediate disc 8 in the declutching
operation. The Belleville ring 154 causes the pressure plate 5 and
intermediate disc 8 to be gripped together resiliently. As mentioned
above, it is dimensioned accordingly.
It will be noted that the pressure plate 5 has radial channels 52, which
are open axially at the level of the intermediate disc 8 and in line with
holes 26 (FIG. 3) formed in the skirt portion 22 of the cover plate 2.
This provides a ventilation facility for the pressure plate 5, which
enables the temperature of the diaphragm 4 to be reduced, so avoiding any
undue deterioration in the resilient characteristics of the diaphragm
under the effect of heat in operation.
It will also be noted that the radial web 111 of the hub 11 is perforated
at 115, FIG. 4, thus reducing the weight of the hub 11 and improving the
ventilation of the latter.
As can be seen in FIG. 6, one of the sides, or lateral edges, 120 of the
tenons 81, 71, 61 of the intermediate discs 8, 7, 6 respectively passes
through the centre of rotation O of the intermediate disc concerned. In
general terms, the axis of symmetry 121 of each tenon does not pass
through the centre of rotation O of the corresponding intermediate disc.
This is important because, in a clutch having two or more discs, their two
sides 50 and 60 (see FIG. 6) will in certain cases not be interchangeable
after the clutch has been refitted.
The arrangement described and shown thus ensures that, during refitting of
the discs 6, 7 and 8, the latter cannot be refitted the wrong way round.
It will be recalled that in the normal position with the clutch engaged,
the diaphragm 4 bears against the bead 24 and on the lip 51 (FIG.2), so
that the pressure plate 5 is urged towards the reaction plate 1 so as to
grip the intermediate discs 6, 7 and 8 and the friction discs 9 and 10
between the pressure and reaction plates. In order to disengage the clutch
(i.e. to perform the declutching operation), it is merely necessary to
apply a thrust by means of a clutch release bearing (not shown) on to the
inner end of the fingers 42 of the diaphragm 4, so as to cause the
diaphragm to tilt and overcome the axial thrust which the diaphragm exerts
on the pressure plate 5.
It will be noted that during declutching, the friction discs 9 and 10 have
sufficient degree of movement, that is to say a gap exists between the
discs 6, 7 and 8 and the friction discs 9 and 10. This is due mainly to
the retention of the disc 6 in the axial direction (as already described),
together with the engagement of the intermediate disc 8 with the pressure
plate 5 which is obtained by means of the fastening devices 15. The
friction discs 9 and 10 are also able to slide freely due to their
mounting on the hub 11, which is achieved with only simple machining.
It will be appreciated that the fitting of the clutch makes use of
sub-assemblies. These are: the sub-assembly consisting of the reaction
plate 1, intermediate disc 6 and intermediate crown 3; the sub-assembly
consisting of the hub 11, the friction discs 9 and 10 and the intermediate
disc 7; the sub-assembly consisting of the pressure plate 5 and
intermediate disc 8; and finally a sub-assembly consisting of the cover
plate 2 and diaphragm 4. After the crown 3 and intermediate disc 6 have
been fitted, it is then only necessary to fit into the mortices 36 the
sub-assembly plate 5 with its intermediate disc 8, and finally to fit the
cover plate 2 with its diaphragm 4.
As will be clear from the foregoing description and from the drawings, the
thickness of the closure ring 31 and the distance between the notches 33
and the base of the mortices 36 will be determined according to the
application to which the clutch is to be put. In particular, it depends on
the thickness of the friction disc 10, which (like the other friction disc
9) is thickened at its base to permit its sliding movement on the hub 11.
Similarly, it will be understood that the arrangements described above
enable resilient means to be easily fitted, with these resilient means
exerting a progressively increasing axial thrust so as to improve the
comfort of the driver and to give good contact between the discs 6 to 10
and good ventilation of the pressure and reaction plates. Such resilient
means may be associated with both the pressure plate 5 and with the
reaction plate 1, and may be identical in shape. For example, and
referring to FIGS. 9 to 13, they may each consist of a corrugated,
resilient metallic ring 200, 300, having three radial lugs 201 on its
outer periphery.
The body of the ring 200, 300 consists of circumferentially alternating
radial portions 202, 203 joined together through oblique folds 205. In
order to achieve standardisation of the rings 200, 300, each lug 201 has
an oblong hole 204. Each hole 204 has two radial side edges which are
joined together through rounded corners. These holes 204 are identical, in
this example, to the holes 156 in the pressure plate 5.
The ring 200, 300 is both light in weight and thin. In this example there
are three of the lugs 201 to each ring, with each lug 201 projecting from
one of the radial portions 202, 203 of the ring. As shown in FIG. 13, the
lugs 201 project from radial portions 203.
Thus the resilient ring 300 associated with the reaction plate 1 comprises
lugs 201 which are arranged to cooperate in a mating manner with the
notches 33 of the closure ring 31, so as to provide a coupling of the
tenon and mortice type. In this case, the rounded stop surface 35 (FIG. 5)
is not mandatory.
The lugs 201 are in contact with the tenons 61, and have a circumferential
width substantially equal to the circumferential width separating the
lateral flanks of the notches 33, with the depth of the latter depending
on the thickness of the ring 300. The ring 300 is centered by means of the
radial notches 33, by virtue of the lateral contact of the lugs 201 with
the notches 33 and the fact that there are three of the latter. This ring
300 is interposed axially between the reaction plate 1 and its adjacent
intermediate disc 6, with the radial portions 202 of the ring being in
contact with the reaction plate 1, and its other radial portions 203 (some
of which are extended by the lugs 201) in contact with the intermediate
disc 6.
The other corrugated resilient metal ring 200 is associated with the
pressure plate 5 and with its adjacent intermediate disc 8. The ring 200
is interposed axially between the plate 5 and disc 8, and is in contact
with the latter through its radial portions 203 and lugs 201. The ring 200
is in contact with the pressure plate 5 through its radial portions 202.
The lugs 201 are in contact with the tenons 81, are are traversed by the
tubes 153, as can clearly be seen in FIG. 11. As shown in FIG. 12, the
tubes 153 come into side contact with the holes 204, enabling thermal
expansion and contraction to be accommodated.
The dimensions and stiffness of the resilient ring 154, which may for
example be in the form of a Belleville ring, are of course preferably
chosen so as not to compress the ring 200 fully in the declutched state
and during declutching, while still enabling the ring 154 to yield axially
in order to accommodate thermal movement of the pressure plate 5.
Similarly, the ring 300, which is arranged to exert the same thrust, does
not become fully compressed in the engaged position of the clutch.
During operation of the clutch, in order to obtain a progressive clutch
engaging action, the rings 200 and 300 are thus compressed resiliently.
The intermediate disc 6 becomes axially displaced, while remaining in
contact with the notches 33.
The resilient rings 200 and 300 may of course be made of different
stiffnesses, so as to exert different thrusts. In this way it is possible
to arrange for the ring 300 associated with the reaction plate to become
compressed first, or vice versa. Preferably, the rings 200 and 300 are not
fully compressed: this enables good ventilation of the discs and of the
pressure and reaction plates to be obtained, as well as good cooperation
of the various surfaces involved.
The rings 200 and 300 may also be different as to the shapes of their lugs
201. The rings may also be flanged. Thus, the radial portions 203 and the
lugs 201 may be in contact with either the reaction plate 1 or the
pressure plate 5, and the radial portions 202 may be in contact with
either one of the intermediate discs 6 and 8.
In a modification, only the reaction plate 1 has a resilient ring 200 or
300 associated with it, the pressure plate 5 not having a resilient ring
associated with it; or vice versa. The profile of the ring 200 or 300 may
be sinusoidal. The tenons 61 may be provided with dowels or bolts for
centring the resilient ring 300. In that case, suitable apertures must be
provided in the reaction plate.
The present invention is of course not limited to the embodiments
described. In particular, the pressure plate may be driven directly in
rotation by the intermediate crown 3, to drive the intermediate disc 8 in
rotation. This arrangement thus involves a reversal of the structures as
described above, with the pressure plate 5 centring the intermediate disc.
The number of securing means or fastening devices 15 may be different from
the number of tenons 81.
The intermediate disc 8 and the pressure plate 5 may both be driven by the
intermediate member 3, in such a way that the tubes 153 are not
necessarily centring tubes. Similarly, the driving of the intermediate
discs may be obtained by means of a hollow member defining a cover, so
that the intermediate member 3 is then no longer essential.
In a further modification, the intermediate disc may include supplementary
tenons, which are distinct from the driving tenons 61 and which alternate
with the latter. These supplementary tenons serve merely for ensuring that
the intermediate disc is engaged with the pressure plate in the same
manner as described above. Thus these supplementary, or coupling, tenons
are not necessarily also drive tenons. In regard to the centring and
spacing means, instead of the tube 153 described above it is possible to
provide a shouldered cylindrical dowel, which is secured directly in the
tenon 81 of the intermediate disc 8, for example adhesively. It is also
possible, in another modification, to use a bolt which engages with the
tenon 81 and which has a smooth shank portion for cooperating with the
side flanks of the hole 156.
The centring means may of course not necessarily also have the function of
a spacing means. In that case it is a separate element from the spacing
tube or the like. In a further modification, a bolt having a smooth shank
portion may be used for centring the pressure plate.
Instead of the member 3, a plurality of spacing blocks may be used. These
spacing blocks are then fixed to the cover plate 2 and to the reaction
plate 1 in the manner described in the specification of French published
patent application No. FR2 623 862A. Between the intermediate discs that
are closest to the reaction plate, these spacing blocks have
circumferential extensions for cooperating with the appropriate
intermediate disc in order to locate the latter axially. In that case, the
thrust surface (e.g. the surface 35) is offset circumferentially with
respect to the rotational driving means itself. Each circumferential
extension or extensions mentioned above, associated with a respective one
of the spacing blocks, may be provided with a notch similar to the notch
33 seen in FIG. 5. Similarly, the base of the notch 33 may constitute the
thrust surface in accordance with the invention, with the relevant face of
the tenon constituting the cooperating reaction surface.
The axial lugs 32 may comprise projections for cooperating with mortices
formed in the discs 7 and 8. In a modification, these lugs comprise dowels
or pins carried by the closure ring 31 and each engaging, with sliding
movement, in a hole formed in a respective one of a series of lugs formed
respectively on the disc 7 and the disc 8.
The clutch may have one friction disc, or more than two. The reaction plate
may cooperate directly with one of the friction discs; in which case the
clutch shown in FIG. 1 will only have two intermediate discs. The clutch
may be of the "pull" type. The pressure plate may be coupled to the cover
plate, for rotation with the latter, by means of tangential tongues, and
may carry its intermediate disc. In that case, the axial lugs serve only
for driving the disc 7.
Finally, the pressure plate may be subjected to the action of engagement
means that comprise a component other than a diaphragm. This may for
example consist of a hydraulic actuator device of the piston and cylinder
type. Alternatively, it may consist of a plurality of coil springs with
declutching levers.
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